Microbes inhabiting the desert respond sensitively to environmental changes and may be an indicator for changes in the desert ecosystem.Hypolithic microbial communities in the desert play a vital role in ecosystem pro...Microbes inhabiting the desert respond sensitively to environmental changes and may be an indicator for changes in the desert ecosystem.Hypolithic microbial communities in the desert play a vital role in ecosystem processes such as soil formation and organic matter accumulation.This study investigated and compared the culturable bacterial community structure and diversity in hypolithic and peripheral soils,and the interaction between bacteria and environmental factors.The bacteria were isolated using four different kinds of media and identified by 16S rRNA gene-sequence analysis.The numbers of culturable bacteria in the hypolithic and peripheral soils ranged from 3.0×104 to 3.6×105 CFU/g and from 6.5×104 to 5.3×105 CFU/g,respectively,indicating that the bacteria number in peripheral soil was higher than that in hypolithic soil.A total of 98 species belonging to 34 genera were identified,among which Arthrobacter,Bacillus,and Streptomyces were found dominantly and widely distributed.The community of culturable bacteria had obvious sample specificity,and the diversity in hypolithic soil was higher than that in peripheral soil.On the regional scale,the distribution of culturable bacteria and the environmental factors showed regular changes.On the local scale,the high heterogeneity of the hypolithic environment determined the specificity of the number and species of culturable bacteria.展开更多
Introduction:Within the Knersvlakte,cyanobacteria occur hypolithically underneath translucent quartz stones in areas with quartz pavement and,outside pavement areas,they are soil-inhabiting within the uppermost millim...Introduction:Within the Knersvlakte,cyanobacteria occur hypolithically underneath translucent quartz stones in areas with quartz pavement and,outside pavement areas,they are soil-inhabiting within the uppermost millimeters of the soil.Both habitats were characterized in terms of biomass and growth patterns of cyanobacteria.Long-term microclimatic conditions were determined.Methods:Biomass of organisms within both habitats was determined by means of chlorophyll analyses.A transect approach was used to determine the frequency of hypolithic growth depending on the size,weight,and embedding depth of the quartz pebbles.Organisms were identified by means of microscopic analyses of the samples.Microclimatic conditions within both habitats,i.e.,temperature,light intensity,air humidity,and soil moisture,were recorded bi-hourly from September 23,2004 through September 7,2006.Results:The biomass of hypolithic and soil-inhabiting crusts was almost identical,88 vs.86 mg Chla/m^(2)and 136 vs.134 mg Chla+b/m^(2).Within the quartz fields,46.8%of the surface area was covered by quartz stones with 69%of translucent quartz stones colonized by hypolithic cyanobacteria and algae.Colonized quartz stones were significantly thicker,heavier,and more deeply embedded in the soil than uncolonized ones.Whereas the annual mean temperature on top of quartz stones was nearly identical to that underneath thin and thick quartz stones,daily temperature amplitudes were largest on the stone surface(up to 48.1K),compared to the hypolithic habitats(up to 39.4K).Light intensity in the hypolithic habitat was between 15 and 30%of the ambient light intensity during daytime.Water condensation in the absence of rain occurred during 50%of the nights on the quartz stone surface,but only during 34%of the nights on the soil surface during winter months within 1 year.Soil moisture beneath quartz layers was greater and less variable than beneath soil-inhabiting crusts.Conclusions:In spite of the large differences in the microclimatic conditions,both habitats seem to be similarly well suited for cyanobacterial growth,resulting in equal biomass values but some differences in taxonomic composition.展开更多
基金financially supported by the National Natural Science Foundation of China(31870479,31570498,and 41801045)the Key Foreign Cooperation Projects of the Bureau of International Cooperation of Chinese Academy of Sciences(131B62KYSB20160014)
文摘Microbes inhabiting the desert respond sensitively to environmental changes and may be an indicator for changes in the desert ecosystem.Hypolithic microbial communities in the desert play a vital role in ecosystem processes such as soil formation and organic matter accumulation.This study investigated and compared the culturable bacterial community structure and diversity in hypolithic and peripheral soils,and the interaction between bacteria and environmental factors.The bacteria were isolated using four different kinds of media and identified by 16S rRNA gene-sequence analysis.The numbers of culturable bacteria in the hypolithic and peripheral soils ranged from 3.0×104 to 3.6×105 CFU/g and from 6.5×104 to 5.3×105 CFU/g,respectively,indicating that the bacteria number in peripheral soil was higher than that in hypolithic soil.A total of 98 species belonging to 34 genera were identified,among which Arthrobacter,Bacillus,and Streptomyces were found dominantly and widely distributed.The community of culturable bacteria had obvious sample specificity,and the diversity in hypolithic soil was higher than that in peripheral soil.On the regional scale,the distribution of culturable bacteria and the environmental factors showed regular changes.On the local scale,the high heterogeneity of the hypolithic environment determined the specificity of the number and species of culturable bacteria.
基金Various forms of assistance from the Universities of Limpopo(South Africa)and Kaiserslautern(Germany)are gratefully acknowledged.We would like to thank Douw Venter,Rudi Wetterman,and Martin Potgieter(University of Limpopo)for their help during the design and installation of the climate stations.Research in the Knersvlakte,South Africa,was conducted with Northern Cape research permits(No.10/2005,ODB 052/2006)and the appending export permits.This project was financed by the German Ministry for Education and Research(BmBF)in the framework of BIOTA South(promotion number 01 LC 0024A).
文摘Introduction:Within the Knersvlakte,cyanobacteria occur hypolithically underneath translucent quartz stones in areas with quartz pavement and,outside pavement areas,they are soil-inhabiting within the uppermost millimeters of the soil.Both habitats were characterized in terms of biomass and growth patterns of cyanobacteria.Long-term microclimatic conditions were determined.Methods:Biomass of organisms within both habitats was determined by means of chlorophyll analyses.A transect approach was used to determine the frequency of hypolithic growth depending on the size,weight,and embedding depth of the quartz pebbles.Organisms were identified by means of microscopic analyses of the samples.Microclimatic conditions within both habitats,i.e.,temperature,light intensity,air humidity,and soil moisture,were recorded bi-hourly from September 23,2004 through September 7,2006.Results:The biomass of hypolithic and soil-inhabiting crusts was almost identical,88 vs.86 mg Chla/m^(2)and 136 vs.134 mg Chla+b/m^(2).Within the quartz fields,46.8%of the surface area was covered by quartz stones with 69%of translucent quartz stones colonized by hypolithic cyanobacteria and algae.Colonized quartz stones were significantly thicker,heavier,and more deeply embedded in the soil than uncolonized ones.Whereas the annual mean temperature on top of quartz stones was nearly identical to that underneath thin and thick quartz stones,daily temperature amplitudes were largest on the stone surface(up to 48.1K),compared to the hypolithic habitats(up to 39.4K).Light intensity in the hypolithic habitat was between 15 and 30%of the ambient light intensity during daytime.Water condensation in the absence of rain occurred during 50%of the nights on the quartz stone surface,but only during 34%of the nights on the soil surface during winter months within 1 year.Soil moisture beneath quartz layers was greater and less variable than beneath soil-inhabiting crusts.Conclusions:In spite of the large differences in the microclimatic conditions,both habitats seem to be similarly well suited for cyanobacterial growth,resulting in equal biomass values but some differences in taxonomic composition.
